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The onset of thermal degradation dictates the maximum temperature at which a polymer can be used. It is an important limitation in how the polymer is manufactured and processed. For instance, polymers become less viscous at higher temperatures which makes injection moulding easier and faster, but thermal degradation places a ceiling temperature ...
Polymers are composed of long molecular chains which form irregular, entangled coils in the melt. Some polymers retain such a disordered structure upon freezing and readily convert into amorphous solids. In other polymers, the chains rearrange upon freezing and form partly ordered regions with a typical size of the order 1 micrometer. [3]
PTFE is a thermoplastic polymer, which is a white solid at room temperature, with a density of about 2200 kg/m 3 and a melting point of 600 K (327 °C; 620 °F). [26] It maintains high strength, toughness and self-lubrication at low temperatures down to 5 K (−268.2 °C; −450.7 °F), and good flexibility at temperatures above 194 K (−79.15 ...
If the melt of an (organic) amorphous polymer is cooled down, it solidifies at the glass-transition temperature T g. On cooling, the hardness of the polymer increases in the neighborhood of T g by several orders of magnitude. This hardening follows the Williams-Landel-Ferry equation, not the Arrhenius equation.
The ability of the system to be readily deformed above its glass transition temperature allows polystyrene (and thermoplastic polymers in general) to be readily softened and molded upon heating. Extruded polystyrene is about as strong as an unalloyed aluminium but much more flexible and much less dense (1.05 g/cm 3 for polystyrene vs. 2.70 g/cm ...
The melting point for average commercial low-density polyethylene is typically 105 to 115 °C (221 to 239 °F). These temperatures vary strongly with the type of polyethylene, but the theoretical upper limit of melting of polyethylene is reported to be 144 to 146 °C (291 to 295 °F). Combustion typically occurs above 349 °C (660 °F).
Perfectly isotactic PP has a melting point of 171 °C (340 °F). Commercial isotactic PP has a melting point that ranges from 160 to 166 °C (320 to 331 °F), depending on atactic material and crystallinity. Syndiotactic PP with a crystallinity of 30% has a melting point of 130 °C (266 °F). [8] Below 0 °C, PP becomes brittle. [9]
Polymer degradation is the reduction in the physical properties of a polymer, such as strength, caused by changes in its chemical composition.Polymers and particularly plastics are subject to degradation at all stages of their product life cycle, including during their initial processing, use, disposal into the environment and recycling. [1]